Bathyopsis fissidens (Cope 1881, Osborn 1913; Eocene) nests between Coryphodon and Uintatherium and has smaller bones on its face.

Some bones reappear in uinthateres that most mammals don't have:

1. The lacrimal originally extended to the naris, but the maxilla rose to meet the nasal and cover up the anterior lacrimal. In uinitathers the typically hidden middle portion of the lacrimal rises between the nasal and maxilla to form the anterior horn.
2. The prefrontal reappears in uintatheres over the orbit.
3. The postfrontal reappears in uintatheres over the posterior orbit and rises to form the anterior of the posterior horn.
4. The postorbital reappears in uintatheres atop the posterior horn.
5. The supratemporal reappears in uintatheres along the posterior base of the posterior horn.

Unitatherium anceps (Leidy 1872, Eocene 37 mya, 4m long, 1.7 m at shoulder) was a bulky basal ungulate and a sister to Coryphodon. Uintatherium had six bony processes over the skull. Wikipedia identifies it only as an herbivorous mammal. The LRT nests it with Arsinoitherium, Phenacodus and Gobiatherium. The tooth arcade of Uintatherium is less complete. The canines enlarge to saber teeth and a diastema appears with the loss of the anterior premolars. The pelvis widens. Five fingers and toes are retained.

Gobiatherium mirificum (Osborn and Granger 1932; middle Eocene) is widely considered a distinct type of uintathere, like Uintatherium. Gobiatherium has a long wide skull and no horns – unless the nearly circular nasal is actually a set of merged nasal horns, as shown here. Note the indented braincase shared with clade members.